Turning off the switches of the A/V gear doesn't physically disconnect your equipment from the mains. Your equipment may be dumping harmonics onto your AC wiring. Maybe it's the flux capacitors in the Odyssey that are finally broken in . Unplug them instead and play "Sherlock Holmes".

During thunderstorms, electrical systems experience large ground currents and transient voltages. These do make their way to the distribution system. Depending on how the power supply of the 600 is designed, it may be influenced by these transients.